As saccharide and silicone compounds, silicone-modified polysaccharides of a type in which polysaccharides are modified by silicone (main skeleton of the molecule is polysaccharide, refer to Patent Documents 1 to 6) and sugar derivative-modified silicones of a type in which a relatively short monosaccharide or oligosaccharide chain is bonded to a silicone chain or a silicone skeleton (main skeleton of the molecule is silicone, refer to Patent Documents 7 to 30) are known.
The former is often a powdery solid and the latter is often a viscous liquid. In general, opacity on the exterior of a powdered product is not a problem, but when a liquid product is cloudy, there may often be a problem of appearance or potential phase separation. Many considerations have been made as described above relating to a chemical structure or the production method of the liquid sugar derivative-modified silicone, but due to the high production difficulty on a commercial scale, there are extremely few commercial products. That is, in general, since there are almost no cases in which an introduction reaction of sugar derivatives with respect to the silicone skeleton proceeds at a chemical equivalent (molar equivalent), normally, the introduction reaction is completed by excessively loading the sugar derivative. Accordingly, an unreacted sugar modifier (sugar derivative) other than a sugar derivative-modified silicone copolymer that is a product remains in a reaction system causing turbidity. Since the sugar derivative has a high boiling point or high molecular weight, purification by stripping is totally ineffective. Therefore, it was extremely difficult to obtain high purity sugar-modified silicones on a commercial scale.
As the production method of the sugar derivative-modified silicone, methods are known in which a sugar derivative having a reactive unsaturated group is added to organohydrogensiloxane (Patent Documents 8 to 10, 13, 17 to 19, and 23 to 28). When molecular weight or weight ratio of silicone moiety in the sugar derivative-modified silicone structure is small, it is easy to obtain a product with little turbidity since the remaining sugar derivative and the sugar derivative-modified silicone are compatible (Patent Documents 10, 18, 19, and 23), but there is a problem in that a range of use is limited since a designable structure is limited. Normally, in many sugar derivative-modified silicones, miscibility of remaining sugar derivatives and sugar derivative-modified silicone products may be low, and the appearance of the product may be cloudy and nonuniform, leading to phase separation during storage after production. Therefore, a purification treatment of removing the remaining sugar derivatives is performed using a technique such as solvent extraction, column chromatography, dialysis, film separation (microfiltration or ultrafiltration), and reprecipitation (Patent Documents 9, 13, and 17 and Comparative Manufacturing Example 6 of Patent Document 30). However, since a large volume of organic solvent or water is necessary for the purification techniques, there is a large problem for waste disposal and efficiency aspects. In addition, there is a problem of limiting the application to a laboratory scale device and not being suitable for mass production on a commercial scale. Microfiltration is one method of filtering fine particles such as colloidal particles that are not able to be filtered using filter paper or the like. There are problems in that since a porous polymer membrane is used, the film tends to be obstructed for a short time at which pore size is small, and that it is necessary to dilute in a large excess of solvent when silicone is generally applied with high viscosity since time is necessary for filtration.
An example is indicated in Patent Document 24 of a compound in which the hydroxyl group is protected is used as the sugar derivative. However, the problem of separation described above is unavoidable even with this technique since deprotection is necessary after the reaction of organohydrogensiloxane ends. A technique for performing deprotection after the protected sugar derivative is introduced to the silicone chain is performing hydrolysis under an environment in which hydrophobicity is increased due to the silicone, and is extremely inefficient. Accordingly, acidizing conditions for deprotection are inevitably harsh and breakage of the silicone backbone occurs. As a result, there is a new problem that the desired product is not obtainable with good reproducibility.
In Example 1 in Patent Document 29, it is reported that xylitol (sugar derivative) co-modified organopolysiloxane that has low viscosity and low HLB is obtained as a transparent liquid by distilling a low boiling point fraction and subjecting to filtration treatment after a hydrosilylation reaction. Since the sugar derivative-modified silicone has extremely low HLB and low viscosity, the affinity between a residual sugar derivative starting material and the produced sugar derivative-modified silicone is extremely poor in a reaction mixture and the residual starting material precipitating due to two layer separation upon leaving to stand for one to two days on a laboratory scale. Therefore, it is possible to obtain good transparency by collecting and filtrating only the phase of a supernatant sugar derivative-modified silicone main body. Accordingly, there are problems of low yield or needing a long time for production and an applicable structure range being narrow. Furthermore, since volume (height) of a reaction mixture is increased in a case of mass production on a commercial scale, there is a problem that a time up to two layer separation is reached is much longer than the laboratory scale and a problem in that an operation in which only the supernatant is filtered is difficult.
As another production method of sugar derivative-modified silicone, techniques are known in which amino-modified silicones are set as a starting material and caused to react (carry out Michael addition) with the sugar derivative containing sugar lactone or an α,β-unsaturated carbonyl group (Patent Documents 7, 11, 12, 16, and 22). However, there is a problem in that an amide bond formed by reaction of an amino group of amino-modified silicone with a sugar lactone is unstable and hydrolysis tends to occur. Since a secondary or tertiary amino group is formed in the reaction of amino-modified silicone and sugar derivatives containing an α,β-unsaturated carbonyl group, there is a concern such as compatibility with formulations thereof and skin irritation.
Patent Document 14 discloses a technique in which epoxy-modified silicone is set as the starting material and reacted with sugar derivatives having the amino groups. Thereby, although stability of hydrolysis is improved, the obtained sugar derivative-modified silicone has a problem in that compounding with a cosmetic product and the like is difficult since coloring is strong and a strong odor of ammonia tends to occur over time. Since the secondary or tertiary amino group is formed, there is a concern such as compatibility with formulations thereof and skin irritation.
Patent Documents 15, 20, and 21 also disclose production methods of special sugar derivative-modified silicone and techniques of purification, but the methods are extremely complex and mass production on a commercial scale is difficult.
As described above, there have been practically no known useful methods for stably producing liquid high-purity sugar derivative-modified silicone or a composition including the same on a commercial scale. Further, there has also been no known technique of increasing purification of liquid sugar derivative-modified silicones which are applicable regardless of the type of sugar modifier and can reasonably accommodate production on a commercial scale. Accordingly, there has been demand for development of a high purity sugar derivative-modified silicone or a composition including the same that is easily produced, and stable as a liquid such that no phase separation or sedimentation of unreacted starting material, or the like occurs after production, and exhibits almost no turbidity, and a method for producing the same.